[en] The invention belongs to devices for shaping magnetic field in the central region of cyclotrons that utilize an axial introduction of an ion source into the acceleration zone through a hole in the electromagnet pole. The purpose of the invention is to enhance the beam intensity by way of improving the conditions for orbit shaping in the central region. This is achieved by shifting a through hole in each electromagnet pole relative to its axis in the direction parallel to the duant edge. The absolute shifting, δ, is less than the hole radius, R, i.e. 0.5 < δ/R < 1.0. The presence of a hole shifted relative to the pole center leads to the occurrence of azimuthal inhomogeneity in the magnetic field of the first harmonic form. The described device has been suggested and realized in the process of shaping the magnetic field in the center of a compact cyclotron. It allowed one to position an ion source having such dimensions which enabled one to obtain the arc in excess of a kilowatt. The isochronous acceleration conditions have been maintained